2009

A rather impressive cut-off low is currently generating a large cloud shield along and ahead of a cold front about 150 miles off the CA coast. There is significant convective could development near the low center, as well. This low is slowly drifting towards the east/northeast, and the associated cold front will lift across NorCal tomorrow. The front may bring brief heavy rain and local thunderstorms, as there is a fair bit of dynamic instability. More substantial convective development could occur  behind the cold front in the afternoon, as surface heating and colder temps aloft  generate steep lapse rates and a continued 140+ kt jet streak acts to enhance vertical shear profiles. Although a widespread severe event is not currently anticipated, this type of pattern is favorable for some convective surprises, so it might be wise to keep an eye to the radars tomorrow. Scattered showers will linger on Wednesday, and there could even be a thunderstorm once again in favored locations. One of the most notable effects of this system will be the much colder temperatures (after today’s 80+ degree readings, highs by midweek may struggle to reach 60 in the north.) Another…colder…system will dive into the state from the northwest on Thursday, bringing more showers…even colder temperatures…and maybe another possibility of convection. The models have trended toward more West Coast troughing in the extended period, so I would expect more unsettled weather at times during the 7-10 day period, with at least occasional chances of convective activity.